According to the official Boston Celtics' Twitter account, Jared Sullinger will not be playing in tonight's game against the Sacramento Kings due to a concussion suffered in last night's game against the Lakers:

Jared Sullinger will not play tonight in Sacramento. He suffered a mild concussion during the fourth quarter of last night's game in L.A.
— Boston Celtics (@celtics) February 22, 2014

It's a mild concussion, so hopefully it's nothing too serious and he will be able to play in future games. According to CSNNE, Sully is listed as day-to-day:

Per @celtics: Jared Sullinger won't play tonight - mild concussion suffered in the 4th quarter of Friday's game in LA. He is day to day.
— Abby Chin (@tvabby) February 22, 2014

Rajon Rondo is also out of tonight's game (rest on the 2nd game of a back-to-back), so Phil Pressey and Brandon Bass will be starting: